Unify detection of temporary directory (bug #62215). Instead of using differing implementations of detecting the temporary directory in multiple functions, use "sys::env::get_temp_directory" (in some of them). * libinterp/corefcn/file-io.cc (Ftempdir): Add implementation wrapping around "sys::env::get_temp_directory" replacing tempdir.m. (Ftempname): Remove local check of environment variable "TMPDIR". (Ftmpfile): Create temporary file in directory given by "sys::env::get_temp_directory". * libinterp/corefcn/gl2ps-print.cc (gl2ps_renderer::draw): Use Octave's functions for opening temporary file. * liboctave/system/oct-env.cc (sys::env::do_get_temp_directory): Check environment variable "TMPDIR" on all platforms. * liboctave/system/lo-sysdep.h, lo-sysdep.cc (sys::fopen_tmp): Add new function to open temporary file that deletes automatically after use. * scripts/miscellaneous/tempdir.m: Remove file that is replaced by DEFUN. * scripts/miscellaneous/module.mk: Remove deleted file from list. * bootstrap.conf, liboctave/wrappers/tmpfile-wrapper.h, tmpfile-wrapper.c, liboctave/wrappers/module.mk: Remove unused module "tmpfile".